Explosive



Patented May 13$, 393$ E. I. du Pont de Nemours &' Co mington, M, a corporation or Wil- No Drawing. Application November 14, 1935,

Serial No. 49,691

10 Claims.

The present invention relates to a free-running explosive of the dynamite type, and more particularly to a free-running dynamite capable of detonation after storage under water.

In many blasting operations, particularly in quarry blasting it is the practice to drill relatively small, vertical bore holes, commonly known as jackhammer holes, in order to reduce the cost of the drilling operation. These holes are then sprung or chambered by shooting a relatively small charge of explosive at the lower end. The chamber thus formed is then loaded with a heavier charge of dynamite and the hole is again sprung, or the rock is blasted down.

For loading bore-holes of this character, dynamite in stick-form is not satisfactory. The channel itself, being small in diameter and frequently devious in path, is apt to be choked or plugged in the loading operation. Moreover, even where the channel itself has not been choked, it is difficult, if not impossible, to avoid large air spaces between the dynamite sticks in the chamber. As a result, an unsatisfactorily low loading density results.

It is much more satisfactory to load bore-holes of this character with a free-running powder which may be poured from a bag down the small bore-hole, and which will easily adapt itself to sary, and therefore nitroglycerin headaches are avoided.

For these reasons, free-running powders of the pulverulent type have been used extensively for loading bore-holes of this character, but heretofore the powders employed have not been waterresistant. As a consequence, failures have frequently occurred-where the bore-holes were partly or completely filled with water. Many attempts have been made to develop a free-running, water-resistant powder, but heretofore the results have not been promising. Small particles 45 ofsmokeless powder or other water-resistant explosives have been tried, but all results seemed to indicate that such small particles of waterresistant explosives could not be detonated under water. Thus, even blasting gelatin, in the form 0 of particles or'%" in diameter, could not be detonated under water by any means. Because of this fact, the attempts to use small particles of gelatin dynamite and the like have generally been abandoned, and the problem has remained unsolved.

The object of the present invention is a new and improved free-running powder. A further object is a free-running powder which can be detonated under water, even after long periods of submersion thereunder. A still further object is a powder of the character described which possesses an inherently high loading density. Other objects will be apparent as the invention is hereinafter more fully described.

I have found that these objects may be accomplished by employing a comminuted plastic explosive such as gelatin dynamite, and the like, the individual particles of which have certain minimum dimensions. An investigation of the problem has revealed the unexpected fact that, although sections of gelatin dynamite which have a minimum dimension less than approximately one-eighth inch will notpropagate detonation through an intervening fllm of water, nevertheless, sections of gelatin which are larger than this critical size will readily do so. The failure of prior investigations of this problem may therefore be ascribed to the failure to recognize this controlling factor.

Although the minimum or critical size of the particles suitable for this purpose'is controlled by the above mentioned factor, the maximum site is controlled by the character of the free-running properties desired. Thus, substantially spherical sections having a diameter of one inch may be satisfactory for certain purposes, whereas for other uses, only the smallest sized particles possible will be suitable. In general, however, I prefer to employ sections, the minimum dimen: sions of which are between one-quarter and one inch.

To prevent the individual sections of plastic explosive from coalescing or sticking together, a material may be used which effectively separates the particles from each other. For this purpose, the particles may be wrapped in sheet material, such as waxed paper, 'or the like. A pulverulent material, such as starch, sawdust, ammonium nitrate, a free-running pulverulent dynamite, or their equivalent may also be employed. According to this method, at least part of the pulverulent material adheres to the surface oi the gelatin dynamite sections, and thereby prevents the coalescence or adherence oithe individual sections.

To achieve the free-running properties which are so highly desirable, sections such as cubes, hexagonal prisms and the like may be satisfactorily employed under certain conditions. where relatively small sections are used, for example.

' ticles.

Here the free-flowing properties will not be greatly affected by the shape of the individual par- In other instances, satisfactory, freeflowing properties may be obtained only if the shape of the individual particles at least approximate that of a sphere. Thus, where large sections are employed, it is advisable to round oi! the corners of the individual portions so that the material will roll readily. For this reason, it is frequently desirable, after at least partly covering the surface with a material which prevents the particles from sticking together, to rumble the comminuted gelatin dynamite for a short time in order to round of! the corners of the sections. By this means, an .excellent, free-running powder is obtained.

In order'to describe my invention more clearly, I may cite the following specific examples which fully illustrate the manner .in which my invention may be carried out. It is understood that this is done solely by way of illustration, and is not to be construed as a limitation as to the scope of my invention.

Example I A 30%ammonia gelatin is cut into, sections V inch square and inch high. This may be accomplished by hand with the aid of an ordinary knife. If desired, the sections may be cut by the process disclosed in co-pending application of N. G. Johnson and G. H. Smith, Serial No. 49,690, flied November 14, 1935, or by the continuous process disclosed in copending application of Wm. E. Kirst and W. E. Lawson, Serial No. 50,101, flied November 18, 1935. The sections thus formed are rolled in sawdust, so that the surface of the explosive is at least partly coated with the sawdust, which prevents the individual sections from sticking together. To round oil! the corners, the sections are tumbled for a. short time with an excess of sawdust. after which the excess sawdust is removed by screening or other suitable means.

The material thus produced may be readily poured from a bag, for example, and will readily run through a funnel provided with a two inch outlet.

The water-resistance of the free-flowing powder thus produced is indicated by the following results of actual tests. In each of several fiveliter glass flasks approximately 4 kg. of this dynamite was placed. One of the flasks was shot immediately. The remaining flasks were filled I with water and shot after the material had soaked for various periods or time. Detonation was accomplished solely by means of a standard No.6 electric blasting cap inserted between the pieces in the flask. The results are tabulated below:

One of the outstanding advantages of' my development is the fact that plastic explosives which can not be satisfactorily extruded in the usual manner may in accordance with my in-, vention be employed. Thus a gelatin dynamite which has no starch, and which has a very high ammonium nitrate content is readily adaptable for my purpose. Material of this character, which is said to have poor "extrudability", may with facility be rolled into sheets and cut by hand, or by the processes disclosed in the copending applications above referred to.

trample II A gelatinous dynamite comprising over ammonium nitrate, for example, is cut into cubes inch on an edge. The cubes are rumbled with an excess of an insoluble metal soap such as calcium or barium stearate, oleate, or the like. The excess soap is removed and the coated particles, which are rounded considerably by the above procedure, have excellent, free-running and waterreslsting properties, the latter being enhanced by the nature of the coating material.

Example III The cubes of Example II are covered with a free-running pulverulent explosive, and subsequently rumbled. In this case it is not necessary to remove the excess pulverulent material employed to prevent the individual particles from coalescing.

Example IV By means of a honey-combed knife, sections having the shape of hexagonal prisms, approximately inch high and /2 inch maximum diameter, are cut from a sheet of the blasting gelatin. The individual sections are wrapped in waxed paper and used directly. No failures to detonate were obtained after 16 hours immersion.

' Example V invention. I intend, therefore, to be limited only in accordance with the following patent claims.

I claim: r 1. A: free-running, water-resistant dynamite comprising comminuted gelatin dynamite, the

individual particles of which have 'a minimum dimension of V and a maximum dimension of and a material separating said individual particles and preventing the coalescence thereof.

2. The dynamite composition of claim 1, in

, which the material separating the particles comprises a sheet material wrapped about the individual particles.

3. The dynamite composition of claim 1, in which the material preventing the coalescence of said individual particles comprises a pulverulent material.

4. A free-running, water-resistant dynamite composition, comprising comminuted gelatin dynamite, the individual particles of which have V a minimum dimension of ,4; inch and a maximum dimension of inch, and free-running sawdust, at least part of which adheres to. the surface of said individual particles and prevents the coalescence thereof.

5. The dynamite composition of claim 4, in which the gelatin dynamite comprises blasting gelatin.

6. The dynamite composition of claim 4, in which the gelatin dynamite comprises blasting gelatin, the particles thereof being substantially spherical in shape and having a diameter of approximately one-haif inch.

7. A free-running explosive comprising a comminuted explosive plastic under atmospheric conditions and a material separating the individual particles oi said plastic explosive and preventing the coalescence thereof sald explosive possessing free-flowing properties which permit pouring said explosive through a pipe 2 inches in diameter, said explosive being capable of selfpropagation of the explosion under water.

8. A free-running water-resistant explosive comprising a comminuted explosive plastic under atmospheric conditions; the individual particles of which have a minimum dimension of V and a maximum dimension less than 2", and a maseparating the individual particles of said gelatin dynamite and preventing the coalescence thereof, said explosive possessing free-flowing properties which permit pouring the same through a pipe two inches in diameter, said explosive being capable of self-propagation of the explosion under water.

NORMAN G. JOHNSON. 

